1. Field of Invention
The invention generally relates to a lens, and more particularly, to a zoom lens.
2. Description of Related Art
As state of the art videoconferencing technologies advance, the need for a high pixel and high quality digital video camera (DVC) and digital camera (DC) has been gradually rising, while trending towards miniaturization, large stops, and wide view angle. In order to achieve large stops and wide view angle within a small space, a significant emphasis is placed on the lens design framework.
However, in current zoom lens designs, due to more manufacturing difficulties and limited by stricter tolerances, these designs cannot concurrently achieve advantages of high resolution, large stops, and wide angle of view. Moreover, insufficient luminous flux, noise accumulation, and underexposure typically results when small stops are applied in digital video cameras used during nighttime. For example, U.S. Pat. Nos. 7,242,529 and 7,110,186 disclose stops having F-numbers above 3.5, which may easily result in insufficient luminous flux.
Moreover, in the zoom lens disclosed by U.S. Pat. No. 7,242,529, not only does the disclosed zoom lens not meet the need of large stops, but a field of view is only 31.9 degrees, resulting in a reduced shooting range and insufficient luminous flux. On the other hand, although the zoom lens disclosed by U.S. Pat. No. 7,177,100 has advantages such as a 3× zoom capability, a wide angle of view, and large stops, the zoom function cannot be accomplished within the lens body, and therefore the lens module cannot be miniaturized.
Furthermore, U.S. Pat. No. 7,623,297 discloses a zoom lens. The zoom lens includes five lens groups, one of the five lens groups is a prism. US Patent Publication No. 20080088943 discloses a zoom lens including four lens groups.